/Engine/Source/Editor/UnrealEd/Classes/ThumbnailRendering/SlateBrushThumbnailRenderer.h
void CreateThumbnailAsImage ( uint32 Width, uint32 Height, [FRenderTarget](API\Runtime\Engine\FRenderTarget) * RenderTarget, [FSlateBrush](API\Runtime\SlateCore\Styling\FSlateBrush) & Brush )